The present invention is related to gas turbine engines, and in particular to a system for positioning variable guide vanes.
Gas turbine engines rely on rotating and stationary components to effectively and efficiently control the flow of air through the engine. Rotating components include rotor blades employed in compressor and turbine sections for compressing air and extracting energy from air after combustion. Stationary components include vanes placed in the airflow to aid in directing airflow. By varying the position of the vanes (i.e., rotating them to vary the profile provided to the airflow), airflow characteristics can be optimized for various operating conditions.
One system for providing actuation of the vanes is a linear actuator connected to the plurality of variable guide vanes via a series of linkages and synchronizing rings. Splice brackets are used to bridge the halves of the synchronizing ring together. Excess deflections of the linkages and/or synchronizing rings will affect system's ability to control the position of the variable vanes accurately. Specifically, deflection of the synchronizing ring causes variation of the vane positions around the vane stage. Typically, adjustable composite bumpers mounted on the inner diameter of the synchronizing ring (along with high synchronizing ring stiffness) are used to limit the radial deflection of the synchronizing ring during normal engine operation conditions. However, under some engine conditions such as engine surge condition, much higher loads can cause excessive deflections of the synchronizing ring. These deflections can result in stresses exceeding the yield strength of the synchronizing ring and adjoining splice brackets. These deflections cannot be accommodated by typical composite bumper designs within the constrained space of some gas turbine engines.